# Screw-jack screw Tr16×4, 90 mm thread, Ø28 head with tommy-bar holes

> What thread does a screw jack use?

- Category: Hardware › Mechanism parts
- Kind: Modern device
- Basis: Xem Studio design following Brown's figure (1868); true size, no printing allowance
- Page: https://xemstudio.com/objects/screw-jack-screw-tr16x4/ · JSON: https://xemstudio.com/api/geometry?object=screw-jack-screw-tr16x4 · Plain text: https://xemstudio.com/objects/screw-jack-screw-tr16x4/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

## Overall (mm)

| length | width | height |
|---|---|---|
| 28.0 | 28.0 | 106.0 |

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- Tr16×4 trapezoidal (ISO 2904 basic profile, 30°) screw, 90 mm of thread, with a Ø28 × 16 head cross-drilled Ø6 both ways for a tommy bar.
- Lift per turn = pitch = 4 mm; with friction coefficient 0.15 a 30° Tr thread at this lead angle (4.5°) is self-locking, so the load stays up.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

## Sizes

| dimension | value |
|---|---|
| thread | Tr16×4, single start, right hand |
| thread length | 90 mm |
| minor Ø (basic) | 12 mm |
| head | Ø28 × 16, 2 × Ø6 cross holes |

## Where the files are

- Henry T. Brown (1868, public domain): [Five Hundred and Seven Mechanical Movements — scan on archive.org](https://archive.org/details/fivehundredseven00browiala) — web — Publisher's page; dimensions are facts
- 507movements.com: [Brown's movement No. 389: figure, his text and an animation](https://507movements.com/mm_389.html) — web — Publisher's page; dimensions are facts
- Xem Studio: [drawing](https://xemstudio.com/objects/screw-jack-mechanism/) — web — Publisher's page; dimensions are facts

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/screw-jack-screw-tr16x4/index.json

- screw-jack-screw-tr16x4: [STEP](https://xemstudio.com/files/hardware/screw-jack-screw-tr16x4/screw-jack-screw-tr16x4.step) · [STL](https://xemstudio.com/files/hardware/screw-jack-screw-tr16x4/screw-jack-screw-tr16x4.stl) — screw, axis Z, thread z 0..90, head z 90..106

## Questions

**What thread does a screw jack use?**

Tr16×4 trapezoidal (ISO 2904 basic profile, 30°) screw, 90 mm of thread, with a Ø28 × 16 head cross-drilled Ø6 both ways for a tommy bar.

## Fits with

- [Screw jack, Tr16×4 (4 mm lift per turn)](https://xemstudio.com/objects/screw-jack-mechanism/)